Rodent brain slices—particularly hippocampal slices—are widely used in experimental investigations of epileptiform activity. Oxygenated artificial cerebrospinal fluid (ACSF) is used to maintain slices in vitro. Physiological or standard ACSF containing 3–3.5 mM K+, 1–2 mM Mg2+, and 1–3 mM Ca2+ generally does not induce population epileptiform activity, which can be induced by ACSF with high K+ (8–10 mM), low Mg2+, or low Ca2+ alone or in combination. While low-Mg2+ ACSF without intentionally added Mg salt but with contaminating Mg2+ (≤ 50–80 µM) from other salts can induce robust epileptiform activity in slices, it is unclear whether such epileptiform activity can be achieved using ACSF with moderately decreased Mg2+. To explore this issue, we examined the effects of moderately modified (m)ACSF with 0.8 mM Mg2+, 1.3 mM Ca2+, and 5.7 mM K+ on induction of epileptiform discharges in mouse hippocampal slices. Hippocampal slices were prepared from young (21–28 days old), middle-aged (13–14 months old), and aged (24–26 months old) C57/BL6 mice. Conventional thin (0.4 mm) and thick (0.6 mm) slices were obtained using a vibratome and pretreated with mACSF at 35–36 °C for 1 h prior to recordings. During perfusion with mACSF at 35–36 °C, spontaneous or self-sustained epileptiform field potentials following high-frequency stimulation were frequently recorded in slices pretreated with mACSF but not in those without the pretreatment. Seizure-like ictal discharges were more common in thick slices than in thin slices. Prolonged exposure to mACSF by pretreatment and subsequent perfusion can induce epileptiform field potentials in mouse hippocampal slices.

中文翻译：

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细胞外 Mg2+、Ca2+ 和 K+ 的适度变化诱导小鼠海马切片的癫痫样活动

啮齿动物脑切片——尤其是海马切片——广泛用于癫痫样活动的实验研究。含氧人工脑脊液 (ACSF) 用于在体外维持切片。含有 3–3.5 mM K+、1–2 mM Mg2+ 和 1–3 mM Ca2+ 的生理学或标准 ACSF 通常不会诱导群体癫痫样活动，这可以由具有高 K+ (8–10 mM)、低 Mg2+、或单独或组合使用低 Ca2+。虽然低 Mg2+ ACSF 没有有意添加 Mg 盐，但受到其他盐的污染 Mg2+ (≤ 50–80 µM) 可以在切片中诱导强烈的癫痫样活动，但尚不清楚使用适度降低 Mg2+ 的 ACSF 是否可以实现这种癫痫样活动。为了探讨这个问题，我们检查了含有 0.8 mM Mg2+、1.3 mM Ca2+ 和 5 的中度修饰 (m)ACSF 的效果。7 mM K+ 诱导小鼠海马切片中的癫痫样放电。海马切片由年轻（21-28 天）、中年（13-14 个月）和老年（24-26 个月） C57/BL6 小鼠制备。使用振动器获得常规的薄 (0.4 mm) 和厚 (0.6 mm) 切片，并在记录前用 mACSF 在 35-36°C 下预处理 1 小时。在 35-36 °C 下用 mACSF 灌注期间，高频刺激后的自发或自我维持的癫痫样场电位经常记录在用 mACSF 预处理的切片中，但在没有预处理的切片中则没有。癫痫样发作期放电在厚片中比在薄片中更常见。通过预处理和随后的灌注长时间暴露于 mACSF 可以在小鼠海马切片中诱导癫痫样场电位。